1. Field of the Invention
The invention relates to solid state matrix photosensors and, especially, to an improvement as regards smearing effect in solid state matrix photosensors of the frame transfer type.
This smearing effect results in pollution, above and below the illuminated zones, in the video signal coming from the sensor. It constitutes one of the main drawbacks of the frame transfer structure.
2. Description of the Prior Art
This problem is conventionally resolved by either placing a shutter in front of the photosensitive zone to prevent any unwanted radiation during the transfer from the image zone to the storage zone, or increasing the vertical transfer frequency to restrict this effect, in proportion to the run time under an illuminated line during the vertical transfer.
The former approach is cumbersome while the latter is difficult to implement, especially for large-sized photosensors where the vertical transfer frequency cannot be increased sufficiently without lowering the quality of performance of the sensor.
An object of the invention is a frame transfer photosensor, which has a modified structure and which enables the elimination of the smearing effect above an illuminated zone in a dark background.